A number of applications in the field of micro-electronics require not only an electrical interaction with the environment but also some kind of mechanical, thermodynamic, fluid dynamic, chemical, radiation or other interaction with the environment. Examples of these applications can be found in the field of sensory devices, in the field of micro-electromechanical systems (MEMS), etc. A mechanical force, pressure, temperature, chemical substance, physical quantity etc. interacts with a dedicated portion of a semiconductor structure to produce a desired effect, e.g. a certain voltage or capacitance, which is a function of the applied physical quantity.
The example of a pressure sensor shall illustrate the technical context in a representative manner for types of applications requiring a similar interaction with the environment. Pressure sensors are typically used to measure the pressure of a liquid or a gas, such as air. Pressure sensors typically provide an output signal that varies based on the pressure sensed by the pressure sensor. One type of pressure sensor includes a stand alone pressure sensor that is coupled or bonded to a sensor surface, such as an application specific integrated circuit (ASIC). Another type of pressure sensor is a pressure capsule (e.g. a poly-silicon plate) that is integrated with a sensor circuit, such as an ASIC, during a back-end-of-line (BEOL) process. The pressure typically interacts with a lamella of the semiconductor structure that extends in a direction parallel to the main surfaces of a substrate of the semiconductor structure. The lamella is typically located in the vicinity of one of the main surfaces of the substrate. Thus, the main surface comprising the lamella needs to be positioned so that it is facing the volume the pressure of which is to be measured.
In alternative designs the lamella has been moved to the interior of the substrate. The pressure is typically conducted to the lamella by a pressure channel which may have a more or less complicated shape, depending on where the inlet of the pressure channel is positioned relative to the lamella.